Hello there, I would say that they are a reliable engine. I own the 66 Delta my father bought brand new and the turbo 400 and the 425 served him very well. In fact (and I swear this to be an absolute fact) he ran the 425 until 1982 then engine had turned over the odometer more than a few times, and when we were on a family trip #4 hit BDC it literally fell through the paper thin cylinder wall. My dad was an industrial mechanic and knew how to baby things. Anyway enough about family history, That engine if it is a four barrel would have to be producing around 340 hp. I will check my GM books to try and give you an exact # . One thing however as a downfall, if you are going to rev the hell out of this thing you will suck the oil pan dry and that ain't a good thing. These are steel crank, Large bore, short stoke engines that produce a **** load of torque. The trick is to keep oil in the oil pan and let them breath. I really like 425's so I may be a little bias but the fact id Toro engine or not (cam angle) these engines perform very well and if some thought is given you shouldn't be dissapointed with anything except how much lighter your wallet is because you didn't build something that is a helluva lot more common. (smallblock chevy) Sorry for talking your ear off but I love these damn OLDSMOBILES!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

VIN DECODE for 1965 THROUGH 1971 MODELS
From 1965 to 1967 the Serial Number identification plate was attached to
the left front body hinge pillar directly below the upper door hinge. From
1968 to 1971 it was attached to the top of dhe instrument panel on the
driver's side and is visible duough the windshield from outside the car.

Hey Brothers, I'll tell you what I am looking at Jdorour good work brother it is nice to see someone doing some good oldsmobile work, NOT SPREADING HORSESHIT........ sorry for the bad language but when it comes to oldsmobiles here in Canada I feel alone when it comes to talking about them..... and I get screwed when I try to buy for them Because they AIN'T A GODDAMN CHEVY... I Love them all.. OLDS, DODGE, CHEVY, PONTIAC, BUICK......Machines are great... God bless AMERICA and CANADA....... We are all the same and ***** the politics....!!!!!!!!!!!

I should have looked at the previous posts.
The 425 is a very good engine. There are some issues to watch for...
The 1965 engines have the old 4GC carb and the cam bank angle on the 1965 and some 1966 blocks have a 45 degree cam bank angle that limits the selection of cams and lifters. The crankshaft/flywheel bolt pattern is different than later engines making flywheels hard to find. But the good stuff is a forged crankshaft and good heads.

The 425 was built from 1965 to 1967 (the 455 replaced the 425 in 1968). In 1965 the 425 was rated at 300HP for the Low Compression 2BBL and 310HP for the High Compression 2BBl. The 4BBL engine was rated at 360HP and the Starfire Engine was rated at 370HP. For 1966 and 1967 the 2BBL engines had the same ratings but the 4BBL engine and the Starfire got a 5HP bump to 365 and 375. The top dog was the '66 and '67 Toronado engine rated at 385HP. Interesting side note - The 1966 Pontiac 421CI 4BBL engine was rated at 338HP and the 421 Tri-Power engines where rated at 356 and 376. Buicks 425CI for 1966 was rated at 360HP wit two 4BBL Crabs. Oldsmobile's 425 was rated at 375 with a single 4BBL Carb. Only Chevy could out do Olds for big block power.
Cheers

The Jetstar 1 is a nice car. They are very rare. Olds only built them for 2 years (64 and 65). The Jetstar 1 (not to be confused with the Jetstar 88) shared engine and driveline with the Starfire. In 1964 it had the 345 horsepower 394CI engine and in 1965 it had the 370 horsepower 425CI engine. There could be any number of reasons your car has a 425:
It may have been replaced with a later engine.
Your car may be a 1965 not a 1964 (model year and Manufacture year are different).
You may have been misinformed about the engine size.

The 330 came out in 1964 and the 425 (along with the 400) came out in 1965.

Sorry, I may be wrong but there are easy ways to tell. If the valve covers have 5 raised ribs running front to rear and 6 bolts, if the intake manifold has a gap underneth with a tin cover over the lifter valley like a Pontiac, if the oil fill tube is bent to the right side it is a 394. If the valve covers do not have any ribs and have 10 bolts, if the intake forms the cover over the lifter valley, if the oil filler tube is straight up and down it is a 425.

The VIN on oldsmobiles prior to 1971 did not indicate the engine installed. The engine code for a 1964 394CID 345HP Starfire/Jetstar I is JS. It should be stamped on the left cylinder head over the center exhaust port (if the engine has been apart it may be on the right head). The engine code for the 1965 and 1966 425CID 370/375HP Starfire/Jetstar I is NS. It will be stamped on the front of the right cylinder head. You may also want to check the engine casting numbers The 394 Block number is on the right rear of the block and will be 585786, The 425 block number will be on the flat spot behind the water pump to the left of the oul fill tube - it should be 381917 or 386525 with a casting code A.

There are a couple of other things that may have happened. Some states titled cars in the year they where sold or manufactured not the model year - So you may have an early 65 - or - someone may have changed the engine at some point.

By the way you may want to get the service manual for the car. It will give you the correct specifics for the car. The web sight you selected is wrong. It does not even have the correct data for my 1966. It lists the 360HP engine that was only available in 1965 and did not list the 375HP engine. It also shows the 345HP 400CID engine for the 1964 442. Everyone knows that the 442 had a 310HP 330CID engine in 1964 and the 400CID did not come out until 1965.

First off I would like to say "Sorry". I was told by a friend who is a big olds " EXPERT " that it was a 425. The guy I got the car from told me it was a 425. When I went to the Gold book it showed the 64 as a 425 so I figured it was a 425. If you look at the pics I posted on the web-site and going by what your telling me then NO it's not a 425. But like a prodical son, I love it just the same.

No need for sorry. I just want to help where I can. Knowing what you have will help you keep the car in good shape. The 394 was the last of the original Rockets. It was an exceptional engine. If you look at the standard production engines from the other GM devisions for 1964 you will find that it made more power than the Caddy 390, Buick 425 and Pontiac 389 unless they had multi-carb setups. The standard Chevy 409 was good for 340HP. The 394 never gets the recognition it should.

Your car is very nice. I love it. The dark green lovely. You have very good taste in cars.